Neutrino Astronomy with KM3NeT
Uli KatzECAP / Univ. Erlangen
28.05.2010
Vulcano Workshop 2010: Frontier Objects in Astrophysics and Particle PhysicsVulcano, Eolian Islands, Italy, 24-29 May 2010
U. Katz: KM3NeT (Vulcano 2010) 2
• Introduction
• Technical solutions: Decisions and options
• Physics sensitivity
• Cost and implementation
• Summary
U. Katz: KM3NeT (Vulcano 2010) 3
The Neutrino Telescope World Map
NEMO
ANTARES, NEMO, NESTOR
joined efforts to prepare
a km3-size neutrino telescope
in the Mediterranean Sea
KM3NeT
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What is KM3NeT ?
• Future cubic-kilometre scale neutrino telescope in the Mediterranean Sea
• Exceeds Northern-hemisphere telescopes by factor ~50 in sensitivity
• Exceeds IceCube sensitivity by substantial factor
• Provides node for earth and marine sciences
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South Pole and Mediterranean Fields of View
> 75%> 25%
2 downward sensitivity assumed
In Mediterranean,visibilityof givensource canbe limitedto less than 24h per day
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The Objectives• Central physics goals:
• Investigate neutrino “point sources” in energy regime 1-100 TeV
• Complement IceCube field of view• Exceed IceCube sensitivity• Not in the central focus:
- Dark Matter- Neutrino particle physics aspects- Exotics (Magnetic Monopoles, Lorentz invariance
violation, …)• Implementation requirements:
• Construction time ≤5 years• Operation over at least 10 years without “major
maintenance”
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Objective: Support 3D-array of photodetectors andconnect them to shore (data, power, slow control)
• Optical Modules• Front-end electronics• Readout, data acquisition, data transport• Mechanical structures, backbone cable• General deployment strategy• Sea-bed network: cables, junction boxes• Calibration devices• Shore infrastructure• Assembly, transport, logistics• Risk analysis and quality control
Technical Design
Design rationale:
Cost-effectiveReliableProducibleEasy to deploy
Unique orpreferredsolutions
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Further Challenges
• Site characteristicsObjective: Measure site characteristics (optical background, currents, sedimentation, …)
• SimulationObjective: Determine detector sensitivity, optimise detector parameters;
• Earth and marine science nodeObjective: Design interface to instrumentation for marine biology, geology/geophysics, oceanography, environmental studies, alerts, …
• ImplementationObjective: Take final decisions (technology and site), secure resources, set up proper management/governance, construct and operate KM3NeT;
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OM “classical”: One PMT, no Electronics
Evolution from pilot projects:• 8-inch PMT, increased
quantum efficiency(instead of 10 inch)
• 13-inch glass sphere(instead of 17 inch)
• no valve(requires “vacuum”assembly)
• no mu-metalshielding
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OM with many Small PMTs
• 31 3-inch PMTs in 17-inch glass sphere (cathode area~ 3x10” PMTs)• 19 in lower, 12 in upper hemisphere
• Suspended by compressible foam core
• 31 PMT bases (total ~140 mW) ((DD))
• Front-end electronics ((B,CB,C))• Al cooling shield and stem ((AA))• Single penetrator• 2mm optical gel
(ANTARES-type)
X
A
B
CC
D
PMT
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Front-End Electronics: Time-over-Threshold
From the analogue signal to time stamped digital data:
…
Threshold 1
Threshold 2
Threshold 3
Time
Am
plit
ude
t1 t2 t3 t4 t5 t6
Front End ASIC
System onChip (SoC)
Analoguesignal
Digitaldata
Ethernet TCP/IPdata link
Shore
FPGA+processorScott chip
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Data Network
• All data to shore:Full information on each hit satisfying local condition (threshold) sent to shore
• Overall data rate ~ 25 Gbyte/s• Data transport:
Optical point-to-point connection shore-OMOptical network using DWDM and multiplexingServed by lasers on shoreAllows also for time calibration of transmission delays
• Deep-sea components:Fibres, modulators, mux/demux, optical amplifiers(all standard and passive)
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DUs: Bars, Strings, Triangles
• Flexible towers with horizontal bars• Simulation indicates that “local 3D
arrangement” of OMs increases sensitivity significantly
• Single- or multi-PMT OMs
• Slender strings with multi-PMT OMs• Reduced cost per DU, similar sensitivity
per Euro
• Strings with triangular arrangementsof PMTs• Evolution of ANTARES concept• Single- or multi-PMT OMs• “Conservative” fall-back solution
Reminder:
Progress in verifying deep-sea technology can be slow and painful
Careful prototype tests are required before taking final decisions
This is a task beyond the Design Study!
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The Flexible Tower with Horizontal Bars
• 20 storeys• Each storey supports 6 OMs in groups of 2• Storeys interlinked by tensioning ropes,
subsequent storeys orthogonal to each other• Power and data cables separated from ropes;
single backbone cable with breakouts to storeys• Storey length = 6m• Distance between storeys = 40 m• Distance between DU base and first storey = 100m
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• Mooring line:• Buoy (empty glass spheres,
net buoyancy 2250N) • Anchor: concrete slab of 1m3
• 2 Dyneema ropes (4 mm diameter)• 20 storeys (one OM each),
30 m distance, 100m anchor-first storey• Electro-optical backbone:
• Flexible hose ~ 6mm diameter• Oil-filled• 11 fibres and 2 copper wires• At each storey: 1 fibre+2 wires• Break out box with fuses at each storey:
One single pressure transition• Star network between master module
and optical modules
The Slender String
New concept, needs to betested. Also for flexible tower
if successful
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Triangle Structure
100
m40
m
19X40 = 760 m
• Evolution from ANTARES concept
• 20 storeys/DU, spacing 40m
• Backbone: electro-optical-mechanical cable
• Reduced number of electro-optical penetrations
• Use ANTARES return of experience
2.3m
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Deployment Strategy
• All three mechanical solutions:Compact package – deployment – self-unfurling
• Eases logistics (in particular in case of several assembly lines)
• Speeds up and eases deployment;several DUs can be deployed in one operation
• Self-unfurling concepts need to be thoroughly tested and verified
• Connection to seabed network by ROV
• Backup solution: “Traditional” deployment from sea surface
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Compactifying Strings
Slender string rolled upfor self-unfurling:
DU
3 triangles
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• DUs move under drag of sea current• Currents of up to 30cm/s observed
• Mostly homogeneous over detector volume
• Deviation from vertical at top:
• Torsional stability also checked
Hydrodynamic Stability d
Current[cm/s]
flexible towerd [m]
slender stringd [m]
trianglesd [m]
30 84.0 83.0 87.0
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• Different DU designs• require different DU distance• differ in photocathode area/DU• are different in cost
Detector Building Blocks
} different„building block
footprints“
Bars, triangle:127 DUs, distance 180/150 m
Slender string:310 DUs, distance 130 m
2 km 2 km
Footprint optimisation is ongoing
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Example: Sensitivity dependence of point-source search on DU distance for flexible towers (for 2 different neutrino fluxes ~E- , no cut-off)
Optimisation Studies
= 2.0
= 2.2
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• Investigate distribution of angle between incoming neutrino and reconstructed muon
• Dominated by kinematics up to ~1TeV
Angular Resolution
kinematics < 0.1°
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Effective Areas (per Building Block)
• Results very similar for hard quality cuts
• Flexible towers with bars and slender strings “in same ballpark”
• Driven by overall photocathode area
Symbols: Flexible towers, different quality cutsLines: Slender lines, different quality cuts
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Cost Estimates: Assumptions
• Estimate of investment cost• no personnel costs included• no contingency, no spares
• Assumptions / procedure:• Quotations from suppliers are not official and subject
to change• Common items are quoted with same price• Sea Sciences and Shore Station not estimated• Estimates worked out independently by expert groups
and carefully cross-checked and harmonised thereafter
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• Result of cost estimates (per building block):
• Assembly man power (OMs, DU…) is roughly estimated to be 10% of the DU cost
Cost Estimates: Results
Concept DU
Cost
(M€)
No. of
DUs
Total DU
Cost
(M€)
Seafloor
Infrastr.
(M€)
Deploy-
ment
(M€)
TOTAL
COST
(M€)
Flexible
towers
0.54 127 68 8 11 87
Slender
strings
0.25 310 76 13 14 103
Triangles 0.66 127 83 8 7 99
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KM3NeT: Full Configuration
• 2 “building blocks” needed to achieve objectives• Increases sensitivity by a factor 2• Overall investment ~220 M€• Staged implementation possible• Science potential from very early stage of
construction on• Operational costs 4-6 M€ per year (2-3% of capital
investment), including electricity, maintenance, computing, data centre and management
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Point Source Sensitivity (1 Year)
Aharens et al. Astr. Phys. (2004) – binned method
R. Abbasi et al. Astro-ph (2009) scaled – unbinned method
Observed Galactic TeV- sources (SNR, unidentified, microquasars) F. Aharonian et al. Rep. Prog. Phys. (2008) Abdo et al., MILAGRO, Astrophys. J. 658 L33-L36 (2007)
KM3NeT(binned)
IceCube
Expected exclusion limits:
Observation of RXJ1713 with 5 within ~5 years
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Candidate Sites
• Locations of thethree pilot projects:• ANTARES: Toulon
• NEMO: Capo Passero
• NESTOR: Pylos
• Long-term sitecharacterisationmeasurementsperformed
• Site decision requiresscientific, technologicaland political input
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Next Steps and Timeline• Next steps: Prototyping and design decisions
• TDR public in ~2 weeks• final decisions require site selection• expected to be achieved in 18 months
• Timeline:
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Conclusions
• A design for the KM3NeT neutrino telescope complementing the IceCube field in its of view and surpassing it in sensitivity by a substantial factor is presented.
• Readiness for construction expected in 18 months
• An overall budget of ~250 M€ will be required. Staged implementation, with increasing discovery potential, is technically possible.
• Within 18 months, remaining design decisions have to be taken and the site question clarified.
• Installation could start in 2013 and data taking soon after.